Hydraulic fracturing is a well stimulation technique designed to increase the productivity of a well by creating highly conductive fractures or channels in the producing formation surrounding the well. The process normally involves two basic steps: (1) injecting a fluid at a sufficient rate and pressure to rupture the formation thereby creating a crack (fracture) in the reservoir rock, and (2) thereafter placing a particulate material (propping agent) in the formation to maintain the fracture walls open by resisting forces tending to close the fracture. If stimulation is to occur, the propping agent must have sufficient mechanical strength to bear the closure stresses and provide relatively high permeability in the propped fracture.
Many hydraulic fracturing treatments consist of elaborate mixtures of gelled fluids and proppants. The degree of success expected from well stimulation using conventional hydraulic fracturing techniques depends on the effective placement of a high permeability proppant and a generated fracture to increase the conductivity of the formation. Many wells are completed in reservoirs which are particularly fluid sensitive. Characteristics of the reservoir (low reservoir pressure, e.g.) may limit the effective application of conventional hydraulic fracturing techniques.
Although a variety of particulate materials are used as proppants, silica sand remains the only material that is used extensively. It has been long recognized, however, that sand is not the ideal proppant. Sand at closure stresses encountered in deep formations tends to disintegrate, producing fines or fragments which can drastically reduce permeability in the propped fracture.
Therefore, what is needed is a hydraulic fracturing method that provides for the effective placement of a high permeability proppant in combination with a fracturing fluid which can be used in fluid sensitive reservoirs and also in reservoirs where conventional hydraulic fracturing techniques can't be utilized.